1. Field of the Invention
The present invention relates to a read technique for a storage media. More particularly, the present invention relates to a method for preventing read-disturb happened in a non-volatile memory and a controller thereof.
2. Description of Related Art
Recently, with quick development of digital cameras, camera cell phones, MP3s and MP4s, requirement for storage media thereof is increased accordingly. In view of all the present storage media, since a flash memory has features of non-volatile, power saving, small size and non-mechanical structure etc., it is suitable for being built within the aforementioned portable multimedia devices. Moreover, since demanding of external products such as small memory cards and flash drives is relatively great, improving of storage volume and reliability of the flash memory becomes a major subject to various flash memory manufacturers.
Generally, the flash memories are grouped into two types according to fabrication precision thereof. It is known that the flash memories fabricated based on low fabrication precision are referred to as single level cell (SLC) flash memories, and the flash memories fabricated based on high fabrication precision are referred to as multi level cell (MLC) flash memories. Wherein, memory volume of the MLC flash memory is higher than that of the SLC flash memory, though utilization reliability of the MLC flash memory is lower than that of the SLC flash memory.
However, if data stored within a same block of the MLC flash memory or the SLC flash memory is repeatedly read, for example, if read times of the data is between a hundred thousand times and a million times, reading error of the data may be occurred, or even the data stored within the block may be lost or becomes abnormal, and such phenomenon is referred to as “read-disturb” to those skilled in the art. Therefore, various manufacturers now devote to develop techniques for preventing such read-disturb phenomenon, so as to effectively suppress a chance of read-disturb.